1. Field of the Invention
The present invention relates generally to sharpening tools and equipment. More specifically, the present invention comprises a scissor sharpening machine which retains the conventional curvature along the length of the scissor blade, while simultaneously providing the proper bevel angle or convex edge across the edge of the blade during the sharpening process.
2. Description of the Related Art
High quality scissors and shears are conventionally constructed with the cutting edges of the blades having a large radius curvature along their lengths, in order to provide a more constant included angle between the two blades as they close upon one another during the cutting operation. The radius of curvature used is nearly universally 800 millimeters, or about 31.5 inches. This is particularly true of scissors and shears used in the hair cutting and beauty salon fields, where the scissors used are nearly always quite costly to purchase and of very high quality.
Some of these scissors may cost as much as a few hundred dollars to purchase. Naturally, the owners of such costly scissors are concerned that when they are periodically sharpened, that the sharpening operation be conducted properly. This is not always the case with many conventional sharpening machines and operations. Many of the existing scissor sharpening machines available do not follow the true curvature along the length of the scissor blade, but rather form a series of straight edges with slight angles therebetween. Other sharpening machines have been constructed to follow the 800 mm curvature along the length of the blade, but cannot provide an accurate bevel angle along the blade edge, or form the required convex curvature of the blade edge where such curvature is required.
The present inventor is aware of various scissor sharpening machines and tools which have been developed in the past. One such device is described in Japanese Patent Publication No. 59-115,151 published on Jul. 3, 1984, comprising a manually powered device having a guide roller for the honing stone with the guide roller having a convex curvature along its length in order to follow the curvature of the blade along the length of its cutting edge. While the angle of the scissor blade may be set to form a specific bevel along the blade edge, there is no means to provide a convex edge, as is required for some scissor blades.
Japanese Patent Publication No. 2-036,057 published on Feb. 6, 1990 describes (according to the drawings and English abstract) two sets of rotary grindstones having a variably adjustable angle between the axes of the two sets. This allows the angle of the cutting edge to be adjusted according to that originally manufactured for the blade. However, this device cannot follow the 800 mm (or other) curvature along the length of a scissor blade, nor can it allow the blade to be rotated about its elongate axis during the sharpening operation in order to form a convex curvature along the cutting edge of the blade.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed. Thus, a scissor sharpening machine solving the aforementioned problems is desired.